1. Field of the Invention
The present invention relates to a heat sink assembly, and particularly to a heat sink assembly having a mounting frame which can readily mount a grease cover to a heat sink.
2. Related Art
As computer technology continues to advance, electronic components such as central processing units (CPUs) of computers are being made to provide faster operational speeds and greater functional capabilities. When a CPU operates at high speed in a computer enclosure, its temperature can increase greatly. It is desirable to dissipate the generated heat quickly, for example by using a heat sink attached to the CPU in the enclosure. This allows the CPU and other electronic components in the enclosure to function within their normal operating temperature ranges, thereby assuring the quality of data management, storage and transfer.
To improve heat conductivity between a heat sink and a CPU, thermal interface material such as thermal grease is often applied to a bottom face of the heat sink. However, thermal grease cannot be applied to the heat sink in advance since it is not solid at ambient temperature and may contaminate surrounding articles or be contaminated by dust or foreign particles before the heat sink is attached to the CPU. Conventionally, the thermal grease is spread onto the heat sink just prior to attachment of the heat sink to the CPU. This operation extends the time needed for said attachment.
To overcome the above problem, various grease covers have been developed. U.S. Pat. No. 6,049,458 discloses a grease cover attached to a bottom face of a heat sink to enclose thermal grease spread on the bottom of the heat sink. The thermal grease cannot be contaminated by dust or foreign particles, and does not contaminate surrounding articles when the heat sink is transported or handled. By using the grease cover, the thermal grease can be applied to the heat sink in advance, thereby simplifying the process of attachment of the heat sink to the CPU. However, the grease cover is attached to the bottom face of the heat sink by adhesive. The adhesive must be cleaned from the heat sink before the heat sink is attached to the CPU. This is unduly inconvenient.
Another difficulty relating to the attachment of a heat sink to a CPU is as follows. Oftentimes, a clip is required for mounting the heat sink to the CPU. In earlier times, a linear type of wire clip was widely used. The linear clip is received in a groove defined between two adjacent medial fins of the heat sink, and is engaged with a circuit board on which the CPU is mounted. However, in many modem applications such as when a large heat sink is used, the linear clip cannot firmly retain the heat sink against the CPU. Accordingly, wider plate-type clips were subsequently developed. The plate-type clip is received in a specially widened groove defined between two adjacent medial fins of a heat sink, and engaged with the circuit board. However, the widened groove takes up space that would otherwise be utilized to provide more fins for the heat sink. In effect, the plate-type clip reduces a heat dissipating area of the heat sink, and reduces the heat dissipating capability of the heat sink. Further, combinations of the plate-type clip with a retention module were developed. The retention module is mounted on a circuit board, and a pair of plate-type clips presses on opposite sides of the heat sink and engages with the retention module. However, use of the retention module increases the number of parts of the assembly, and inflates costs.